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Forum Index : Microcontroller and PC projects : Does Maximite need a power supply?
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donmck Guru  Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
My wife's camera. She doesn't know about daylight savings yet. She doesn't know about a lot of things, thanks God! 
Cheers Don... https://www.dontronics.com |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
OH, and according to the operational manual, the green LED is for.......... Well, there is no operational manual. But then, there is no Green LED, as only the Red LED lights up when you plug it in. But then, when you plug in a load, the Green LED comes on. So the Red LED is power in, and the green LED is power out. Actually it is pretty nifty. I love status LEDs and this ticks all the boxes. All it needs is a LED to say it is off. 
Cheers Don... https://www.dontronics.com |
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stuarts Senior Member  Joined: 15/06/2011 Location: AustraliaPosts: 199 |
Don, one of mine charges my phone, Unfortunately it appears to be not quite up to the job of running a Maximite. I'm only getting 2.1 volts with the maximite plugged in. It appears to power up and the SDCARD led flashes booting the autorun and seems to sometimes try to run the program. This program is flashing leds via I2C. No keyboard or display connected. I wonder how they would cope paralleled up? Maybe what we have is a $1.18 box that we can fit our own electronics to. Any thoughts as to a small power supply that can supply about 500ma to power some external electronics too? Stuart Time is nature's way of keeping everything from happening all at once. |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
I am still struggling with the price and postage, even if they aren't 500ma. 18 Y= yuan (CNY) is about $2.50AUD. We paid $3.54AUD, so that is a profit of about 35 cents each for the middle man. How many middle men can you get to the 35 cents? And that's not counting the manufacturer. So they don't really work. The 500ma is a wee bit of a lie! Perhaps we should look for an upmarket one at say $2 each? Cost you more in power boards to double them up. I'll bet there are still some cheap good ones around. Cheers Don... https://www.dontronics.com |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Well, I tried two of these units, and plugged in a VGA monitor and Keyboard, and they both fired up. One read +5.18V, and the other +5.19V I taped Mr Ugly together and he worked too, at 4.97V. So they all seem to be within specs. Did you try your others Stuart? Cheers Don... https://www.dontronics.com |
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Glenn Newbie  Joined: 14/06/2011 Location: AustraliaPosts: 29 |
Heck, I bought three also on a similar basis, but not yet arrived. glenn VK3PE |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Reason I got three was that dealextreme.com give a discount for three, and when you are spending a dollar per item, three seems like a good round figure. Well, a good binary figure, as it is precisely half way between 2 and 4. 
If four of us did this, it must be right. 
Cheers Don... https://www.dontronics.com |
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| stuarts Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 199 |
Don, maybe I should plug it into a screen and keyboard and remove the I2C devices I had connected and try again. Stuart Time is nature's way of keeping everything from happening all at once. |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Did you try all three Stuart, and they all failed? I tried with VGA and KBD, and no I/O, just an SD card. Didn't think your I2C stuff would draw a lot. You have what, 4.7K to +V3.3 on two lines, and whatever your PCF chips are dragging. Perhaps these $1 things need to face a proper load test. Cheers Don... https://www.dontronics.com |
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haiqu Senior Member Joined: 30/07/2011 Location: AustraliaPosts: 152 |
I like your idea Don. It saves a plug, a regulator, a switch and a 330nF cap. Good stuff. But don't buy THAT power supply. It's bloody dangerous. Has a tendency to pop apart to expose live 240V wiring, and the pins aren't insulated. Rob unzip, strip, touch, finger, grep, mount, fsck, more, yes, fsck, fsck, fsck, umount, sleep |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
That is what I didn't like about it Rob, I was about to see where I could wedge a screwdriver into the side of the case, and was simply twisting it a little for movement, and it fell apart. A two year old could pull it apart. You wouldn't want to stand on it. We need to find a decent one, even if we have to double the price.
Cheers Don... https://www.dontronics.com |
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| haiqu Senior Member Joined: 30/07/2011 Location: AustraliaPosts: 152 |
Mine fell apart when I dropped it 2 feet onto a tile floor. It contains what looks like a 1N4148 diode, a tiny choke or transformer, an 8-pin power management chip and some passives. Pretty basic, no isolation. Eek! These things would never meet our electrical standards. But they are cheap... Even worse are the kind with folding pins. I had one explode and take out a $50.00 Bluetooth GPS unit I had on charge. Rob unzip, strip, touch, finger, grep, mount, fsck, more, yes, fsck, fsck, fsck, umount, sleep |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Like I said, a two year old could break the case on these. That's another fine mess you got me into Ollie! $3.54, I could have got half a beer for that. Cheers Don... https://www.dontronics.com |
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| stuarts Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 199 |
Don, is it a choke or a transformer. I wonder if its a switchmode supply. Haven't had chance to look up the specs on the PC. Stuart Time is nature's way of keeping everything from happening all at once. |
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| aargee Senior Member Joined: 21/08/2008 Location: AustraliaPosts: 255 |
Not having seen one in the flesh, as it were, and going by Don's photo - here's my take on the 'design'... 1. Crude half wave rectifier with filter capacitor 2. Basic transistor oscillator to drive 3. the isolation transformer at high frequency (hence it's small size). 4. Opto-isolator for voltage control feedback. 5. Regulator/rectifier for output voltage. One LED indicating "on" and one LED indicating current being drawn. Not sure how this would comply (probably not) with our electrical standards. For crying out loud, all I wanted to do was flash this blasted LED. |
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sparkey Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 819 |
i know this prolly aint the place for this... :the vteck emb bord has not missesed a beat hav it running for around twelve hours now ...thanks and regards sparkey,,, :and yes theres not much to those switching plug packs technicians do it with least resistance |
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| sparkey Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 819 |
yes there pretty cut and shut for the purpose i dont like switchmode`s as a rule but u carnt stop progress ..and don g`day... technicians do it with least resistance |
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| haiqu Senior Member Joined: 30/07/2011 Location: AustraliaPosts: 152 |
Mmmm, beer. I just bought a different type, will let you know what I think of it when it arrives. Still doesn't have insulated pins but if the case doesn't fall apart it might be a goer. Cost me a whole $1.38 but they can be had cheaper. http://www.ebay.com.au/itm/USB-Home-Wall-AC-Charger-Apple-iP od-iPhone-DB3-/220748143328?pt=AU_MobilePhoneAccessories&has h=item33659d5ae0 Rob unzip, strip, touch, finger, grep, mount, fsck, more, yes, fsck, fsck, fsck, umount, sleep |
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| haiqu Senior Member Joined: 30/07/2011 Location: AustraliaPosts: 152 |
Don, The white one is a much better product. Survived the drop test and I couldn't easily pry it open without fear of breaking something. It's also rated at 1000mA. FYI. Rob unzip, strip, touch, finger, grep, mount, fsck, more, yes, fsck, fsck, fsck, umount, sleep |
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| sparkey Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 819 |
i think that the problem lies with the on board 5 volt rail a 7805 can only provide approx 1 amp... A lot of addons will require extra current ... and the maxi should be provided with its basic 1.5 amp power supply.. and a second tapping allowing for at least three amps on a 5 volt rail that comes from the transformer .. ..and a second tapping of a regulated 12..volt rail ..at "lets say 2 amps " a external power supply ..hence to say i think that thius would surfice any number of addon`s in the future....also i dont think that there will be much call for the 3point 3 volt rail but given this another rail at 3 point 3 volt for those who require it,,,...regards sparkey...i would also like to take the time to point out that "rohans " bread board requires 14 volt input ..given that most of the 78XX series can cope quite fine with a voltage input of at least 20 volts ..actully its 40 volts approx ..but what is needed is current regulation and the volts r not the problem ...dont forget its all about current guy`s //gals technicians do it with least resistance |
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